Reamer

ABSTRACT

A reamer incudes a core and a plurality of outer-circumference cutting edges provided on an outer circumference of the core and made of a hard tool material. The core extends from a front end to a rear end. The core is provided with a plurality of flutes from the front end to the rear end. A center-of-gravity adjustment portion, which adjusts a distance from a center of rotation to a center of gravity, is provided at least partially from terminal ends of the plurality of flutes on a rear end side to the rear end of the core. The center-of-gravity adjustment portion causes the deviation of the center of gravity from the center of rotation to be smaller than when no center-of-gravity adjustment portion is provided.

TECHNICAL FIELD

The present invention relates to reamers. The present application is acontinuation of U.S. application Ser. No. 16/973,716 filed on Dec. 9,2020, which claims a priority based on Japanese Patent Application No.2018-123495 filed on Jun. 28, 2018, the entire contents of which areincorporated herein by reference.

BACKGROUND ART

Reamers have conventionally been disclosed in PTL 1 (Japanese PatentLaying-Open No. 2006-88242), PTL 2 (Japanese Patent Laying-Open No.2011-62790), and PTL 3 (Japanese Patent Laying-Open No. 2016-32863).

CITATION LIST Patent Literature

PTL 1: Japanese Patent Laying-Open No. 2006-88242

PTL 2: Japanese Patent Laying-Open No. 2011-62790

PTL 3: Japanese Patent Laying-Open No. 2016-32863

SUMMARY OF INVENTION

A reamer according to an aspect of the present invention includes a coreand a plurality of outer-circumference cutting edges provided on anouter circumference of the core and made of a hard tool material, thecore extending from a front end to a rear end, the core being providedwith a plurality of flutes extending from the front end to the rear end,a center-of-gravity adjustment portion being provided at least partiallyfrom terminal ends of the plurality of flutes on the rear end side tothe rear end of the core, the center-of-gravity adjustment portionadjusting a distance from a center of rotation to a center of gravity,the center-of-gravity adjustment portion causing the distance from thecenter of rotation to the center of gravity to be smaller than when thecenter-of-gravity adjustment portion is not provided.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a front view of a reamer according to Embodiment 1.

FIG. 2 is a plan view of the reamer as viewed from the directionindicated by the arrow II in FIG. 1 .

FIG. 3 is a bottom view of the reamer as viewed from the directionindicated by the arrow III in FIG. 1 .

FIG. 4 is a perspective view of the reamer according to Embodiment 1.

FIG. 5 is a left lateral view of the reamer as viewed from the directionindicated by the arrow V in FIG. 1 .

FIG. 6 is a right lateral view of the reamer as viewed from thedirection indicated by the arrow VI in FIG. 1 .

FIG. 7 is a sectional view taken along the line VII-VII in FIG. 1 .

FIG. 8 shows a deviation of the center of gravity from the center ofrotation of the reamer in the cross section shown in FIG. 7 .

FIG. 9 is a sectional view taken along the line IX-IX in FIG. 1 .

FIG. 10 shows a deviation of the center of gravity from the center ofrotation of the reamer in the cross section shown in FIG. 9 .

FIG. 11 is a sectional view taken along the line XI-XI in FIG. 1 .

FIG. 12 shows a deviation of the center of gravity from the center ofrotation of the reamer in the cross section shown in FIG. 11 .

FIG. 13 is a sectional view taken along the line XIII-XIII in FIG. 1 .

FIG. 14 shows a deviation of the center of gravity from the center ofrotation of the reamer in the cross section shown in FIG. 13 .

FIG. 15 is a front view of a reamer according to Embodiment 2.

FIG. 16 is a plan view of the reamer as viewed from the directionindicated by the arrow XVI in FIG. 15 .

FIG. 17 is a bottom view of the reamer as viewed from the directionindicated by the arrow XVII in FIG. 15 .

FIG. 18 is a perspective view of the reamer according to Embodiment 2.

FIG. 19 is a left lateral view of the reamer as viewed from thedirection indicated by the arrow XIX in FIG. 15 .

FIG. 20 is a sectional view taken along the line XX-XX in FIG. 15 .

FIG. 21 is a sectional view taken along the line XXI-XXI in FIG. 15 .

FIG. 22 is a sectional view taken along the line XXII-XXII in FIG. 15 .

FIG. 23 is a plan view of a workpiece provided with holes.

FIG. 24 is a sectional view of the workpiece provided with the holes.

DESCRIPTION OF EMBODIMENTS Problem to be Solved by the PresentDisclosure

A conventional reamer may fail to reduce cylindricity and roundness of aworkpiece.

The present invention has been made to solve the above problem, andtherefore has an object to provide a reamer capable of reducingcylindricity and roundness of a workpiece.

Effects of the Present Disclosure

The present invention can provide a reamer capable of reducingcylindricity and roundness of a workpiece.

Description of Embodiments the Present Invention

First, embodiments of the present invention are listed and described.

A reamer according to an aspect of the present invention includes a coreand a plurality of outer-circumference cutting edges provided on anouter circumference of the core and made of a hard tool material, thecore extending from a front end to a rear end, the core being providedwith a plurality of flutes extending from the front end to the rear end,a center-of-gravity adjustment portion being provided at least partiallyfrom terminal ends of the plurality of flutes on a rear end side to therear end of the core, the center-of-gravity adjustment portion adjustinga distance from a center of rotation to a center of gravity, thecenter-of-gravity adjustment portion causing the distance from thecenter of rotation to the center of gravity to be smaller than when thecenter-of-gravity adjustment portion is not provided.

In the reamer configured as described above, the center-of-gravityadjustment portion that adjusts the position of the center of gravityfrom the center of rotation is provided at least partially from theterminal ends of the plurality of flutes on the rear end side to therear end of the core, and the center-of-gravity adjustment portion isprovided in such a part, and accordingly, is positioned so as not tocontact a workpiece in cutting. This enables adjustment of the center ofgravity without affecting cutting performance

Preferably, the center-of-gravity adjustment portion is the terminalends of the plurality of flutes, where the terminal ends are provided atdifferent positions in an axial direction. In this case, thecenter-of-gravity adjustment portion can be formed by providing theterminal ends of the plurality of flutes at different positions. Thiscan provide the center-of-gravity adjustment portion with a simpleconfiguration.

Preferably, the center-of-gravity adjustment portion is a lightenedportion provided at a terminal end of one of the plurality of flutes. Inthis case, the center-of-gravity adjustment portion can be provided bymerely removing the material of a part of the core.

Preferably, the core has a shank that held by a machine tool, and thecenter-of-gravity adjustment portion is provided in the shank. In thiscase, since the shank is provided with the center-of-gravity adjustmentportion, the center-of-gravity adjustment portion can be provided atvarious positions in the shank, leading to enhanced flexibility ofdesign.

Preferably, the plurality of outer-circumference cutting edges havefirst to third outer-circumference cutting edges adjacent to each other,and a phase difference between the first and second outer-circumferencecutting edges is smaller than a phase difference between the second andthird outer-circumference cutting edges. Although in this case, thefirst to third cutting edges are disposed at irregular intervals, andaccordingly, the center of gravity easily deviates from the center ofrotation, the center of gravity can be adjusted by the center-of-gravityadjustment portion.

Preferably, the center-of-gravity adjustment portion is provided at aphase corresponding to between the first and second outer-circumferencecutting edges. Although in this case, since the phase is small betweenthe first and second cutting edges, the center of gravity is easilybiased toward between the first and second cutting edges, thecenter-of-gravity adjustment portion provided at the phase correspondingto between the first and second cutting edges can adjust the center ofgravity.

Embodiment 1

FIG. 1 is a front view of a reamer according to Embodiment 1. FIG. 2 isa plan view of the reamer as viewed from the direction indicated by thearrow II in FIG. 1 . FIG. 3 is a bottom view of the reamer as viewedfrom the direction indicated by the arrow III in FIG. 1 . FIG. 4 is aperspective view of the reamer according to Embodiment 1. FIG. 5 is aleft lateral view of the reamer as viewed from the direction indicatedby the arrow V in FIG. 1 .

As shown in FIGS. 1 to 5 , a reamer 90 includes a core 80 and aplurality of outer-circumference cutting edges 11 to 15, which areprovided on the outer circumference of core 80 and made of diamond orCBN, which is a hard tool material. Core 80 extends from a front end 82to a rear end (shank 87) of reamer 90. Core 80 is provided with aplurality of flutes 21 to 25 from front end 82 to the rear end of core80. A lightened portion 29, which serves as a center-of-gravityadjustment portion that adjusts a deviation of the position of thecenter of gravity from the center of rotation, is provided at leastpartially from the terminal end of flute 21 on the rear end side to arear end of core 80. The center-of-gravity adjustment portion causes adeviation from the center of gravity to be smaller than when thecenter-of-gravity adjustment portion is not provided.

Shank 87 has a circular cylindrical shape in the present embodiment, buthas any other shape, such as a rectangular cylindrical shape, atruncated cone shape, or a truncated pyramid shape.

Flutes 21 to 25 extend linearly in parallel with the axis of rotation inthe present embodiment. However, flutes 21 to 25 may extend in a curve.Further, flutes 21 to 25 may extend linearly while inclining toward theaxis of rotation. Flutes 21 and 23 each have a length L1, which islarger than a length L2 of flute 24.

A region with a predetermined length from front end 82 of reamer 90 is acutting edge effective region 80 a, a region of reamer 90 on the rearend side is a chuck region 80 c, and a region between these regions is abalance adjustment region 80 b.

In the present embodiment, an angle between outer-circumference cuttingedge 11 and outer-circumference cutting edge 12 is 60°, an angle betweenouter-circumference cutting edge 12 and outer-circumference cutting edge13 is 60°, an angle between outer-circumference cutting edge 13 andouter-circumference cutting edge 14 is 60°, an angle betweenouter-circumference cutting edge 14 and outer-circumference cutting edge15 is 90°, and an angle between outer-circumference cutting edge 15 andouter-circumference cutting edge 11 is 90°. However, angles other thanthese angles may be provided.

A hard tool insert 19 has outer-circumference cutting edges 11 to 15 andmargins 18, each of which is provided on the rear side of acorresponding one of outer-circumference cutting edges 11 to 15 in therotational direction. Margin 18 is a part that contacts the workpiece inrotary cutting. Referring to FIG. 2 , margin 18 is formed of hard toolinsert 19 and a platform. However, margin 18 may be formed of hard toolinsert 19 alone.

FIG. 6 is a right lateral view of the reamer as viewed from thedirection indicated by the arrow VI in FIG. 1 . As shown in FIG. 6 ,core 80 is provided with an oil hole 81. Oil hole 81 extends in theaxial direction of core 80.

FIG. 7 is a sectional view taken along the line VII-VII in FIG. 1 . FIG.8 shows a deviation of the center of gravity from the center of rotationof the reamer in the cross section shown in FIG. 7 . As shown in FIGS. 7and 8 , a center of gravity 86 in the cross section deviates from acenter of rotation 85, which is the axis of rotation, in the x-axisdirection and the y-axis direction. In this cross section, the center ofgravity deviates toward outer-circumference cutting edges 11 to 13. Thisis because the ratio of core 80 is larger on the side on whichouter-circumference cutting edges 11 to 13 are provided.

FIG. 9 is a sectional view taken along the line IX-IX in FIG. 1 . FIG.10 shows a deviation of the center of gravity from the center ofrotation of the reamer in the cross section shown in FIG. 9 . As shownin FIGS. 9 and 10 , center of gravity 86 in the cross section deviatesfrom center of rotation 85 in the x-axis direction and the y-axisdirection. In this cross section, the center of gravity deviates towardflutes 21 to 23. This is because the ratio of core 80 is larger on theside on which flutes 21 to 23 are provided.

FIG. 11 is a sectional view taken along the line XI-XI in FIG. 1 . FIG.12 shows a deviation of the center of gravity from the center ofrotation of the reamer in the cross section shown in FIG. 11 . As shownin FIGS. 11 and 12 , center of gravity 86 in the cross section deviatesfrom center of rotation 85 in the x-axis direction and the y-axisdirection. In this cross section, the center of gravity deviates towardflute 24 from the following reason. Since lightened portion 29 is formedand flute 24 is smaller, the ratio of core 80 is larger on the flute 24side.

FIG. 13 is a sectional view taken along the line XIII-XIII in FIG. 1 .FIG. 14 shows a deviation of the center of gravity from the center ofrotation of the reamer in the cross section shown in FIG. 13 . As shownin FIGS. 13 and 14 , center of gravity 86 in the cross section deviatesfrom center of rotation 85 in the x-axis direction and the y-axisdirection. In this cross section, center of gravity 86 deviates oppositeto lightened portion 29. Although lightened portion 29 is a part havinga rotational diameter smaller than that of its surrounding part,lightened portion 29 differs from flutes 21 to 25. Flutes 21 to 25 havethe function of removing chips, whereas lightened portion 29 does nothave the function of removing chips. Lightened portion 29 may be acurved surface or a plane (with a curvature of zero).

In Embodiment 1, the center-of-gravity adjustment portion is theterminal ends of flutes 21 to 25, which are provided at differentpositions in the axial direction. In other words, the center-of-gravityadjustment portion may be configured by providing the terminal ends(e.g., 21 a) of flutes 21 to 25 at different positions without lightenedportion 29.

Outer-circumference cutting edges 11 to 15 have first to thirdouter-circumference cutting edges 12, 11, and 15 adjacent to each other,and a phase difference between first and second outer-circumferencecutting edges 12 and 11 is smaller than a phase difference betweensecond and third outer-circumference cutting edges 11 and 15. Lightenedportion 29 is provided at a phase corresponding to betweenouter-circumference cutting edges 11 and 12.

Embodiment 2

FIG. 15 is a front view of a reamer according to Embodiment 2. FIG. 16is a plan view of the reamer as viewed from the direction indicated bythe arrow XVI in FIG. 15 . FIG. 17 is a bottom view of the reamer asviewed from the direction indicated by the arrow XVII in FIG. 15 . FIG.18 is a perspective view of the reamer according to Embodiment 2. FIG.19 is a left lateral view of the reamer as viewed from the directionindicated by the arrow XIX in FIG. 15 .

As shown in FIGS. 15 to 19 , reamer 90 includes core 80 andouter-circumference cutting edges 11 to 15 provided on the outercircumference of core 80 and made of diamond or CBN, which is a hardtool material. Core 80 extends from front end 82 to the rear end (shank87) of reamer 90. Core 80 is provided with flutes 21 to 25 from frontend 82 to the rear end of core 80. A hole 87 a, serving as acenter-of-gravity adjustment portion that adjusts a deviation of theposition of the center of gravity from the center of rotation, isprovided in a part of shank 87 at least partially from terminal end 21 aof flute 21 on the rear end side to the rear end of core 80. Thecenter-of-gravity adjustment portion causes a deviation of the center ofgravity from the center of rotation to be smaller than when thecenter-of-gravity adjustment portion is not provided.

FIG. 20 is a sectional view taken along the line XX-XX in FIG. 15 . FIG.21 is a sectional view taken along the line XXI-XXI in FIG. 15 . FIGS.20 and 21 respectively correspond to FIGS. 7 and 9 .

FIG. 22 is a sectional view taken along the line XXII-XXII in FIG. 15 .As shown in FIG. 22 , shank 87 is provided with hole 87 a. Hole 87 alightens the part at which hole 87 a is provided, and accordingly, thecenter of gravity deviates opposite to hole 87 a.

Core 80 has shank 87 that is held by a tool machine, and shank 87 isprovided with hole 87 a serving as the center-of-gravity adjustmentportion.

Comparative Example: Aluminum Alloy was Processed with PolycrystallineDiamond

TABLE 1 Amount Sample of eccen- Round- Cylin- No. Tool tricity mm nessdricity 1 Without lightened portion 0.174 B B 2 Without lightenedportion 0.052 B B 3 With lightened portion 0.049 A A 4 With lightenedportion 0.032 A A 5 With lightened portion 0.030 AA AA 6 With lightenedportion 0.001 AA AA

First, reamers 90 (samples 1 and 2) of the shape of reamer 90 ofEmbodiment 1 without lightened portion 29 were prepared. Core 80 is madeof cemented carbide. Hard tool insert 19 is made of polycrystallinediamond.

An amount of eccentricity in reamer 90 (a distance from the axis ofrotation to the position of the center of gravity of reamer 90) wasmeasured.

The amount of eccentricity is measured as follows. First, a reamer isattached to a high-accuracy tool balancer. An example of thehigh-accuracy tool balancer is Tool Dynamic TD Comfort available fromHAIMER.

When reamer 90 is rotated, a figure of imbalance is displayed. Forexample, 14.3 gmm is displayed. The mass of reamer 90 is measured. Forexample, it is assumed that the reamer has a mass of 200 g. An amount ofeccentricity can be obtained by dividing the amount of imbalance by themass of a tool. In the above example, the amount of eccentricity is 14.3gmm/200 g=0.0715 mm.

Samples 1 and 2 have amounts of eccentricity shown in Table 1.

Subsequently, a work test was performed using samples 1 and 2. FIG. 23is a plan view of a workpiece provided with holes. FIG. 24 is asectional view of the workpiece provided with the holes. As shown inFIGS. 23 and 24 , first, holes 101 were formed in a workpiece 100 (ADC12(JIS H 5302 2006)) with a drill. Holes 101 were processed with reamers90 being samples 1 and 2, to thereby form finished holes 102. Table 2shows the conditions for creating finished holes 102.

TABLE 2 Evaluation conditions Workpiece ADC12 (JIS H 5302 2006) Cuttingfluid Water-soluble emulsion (8%) Blade diameter ϕ12.000 mm Cutting rateVc = 200 m/min Feed rate f = 0.3 mm/rev

The roundness and cylindricity of finished hole 102 were measured inaccordance with the requirements in JIS B0621 (1984) with a roundnessand cylindrical profile measuring instrument (e.g., RONDCOM 65Aavailable from Tokyo Seimitsu Co., LTD.). Measured data is a numericalvalue measured by the minimum zone circle (MZC) method. Table 1 showsthe results.

Table 3 shows the contents of evaluation criteria (AA, A, B) ofroundness and cylindricity in Table 1.

TABLE 3 Roundness Cylindricity B Not less than 5 μm B Not less than 6 μmA Not less than 3 μm and A Not less than 4 μm and less than 5 μm lessthan 6 μm AA Less than 3 μm AA Less than 4 μm

Example: Aluminum Alloy was Processed with Polycrystalline Diamond

Reamers 90 (samples 3 to 6 in Table 1) of the shape of reamer 90 ofEmbodiment 1 with lightened portion 29 were prepared. Core 80 is made ofcemented carbide. Hard tool insert 19 is made of polycrystallinediamond.

An amount of eccentricity in reamer 90 (a distance from the axis ofrotation to the position of the center of gravity of reamer 90) wasmeasured. Table 1 shows amounts of eccentricity.

Subsequently, a work test was performed using samples 3 to 6. As shownin FIGS. 23 and 24 , first, holes 101 were formed in workpiece 100(ADC12 (JIS H 5302 2006)) with a drill. Holes 101 were processed withreamers 90 being samples 3 to 6, to thereby form finished holes 102.Table 2 shows the conditions for creating finished holes 102.

The roundness and cylindricity of finished hole 102 were measured. Table1 shows the results.

As shown in Table 1, in samples 3 to 6 provided with a lightenedportion, an amount of eccentricity was 0.05 mm or less, and accordingly,roundness and cylindricity were rated “A” or “AA”. It was found that insamples 1 and 2 without a lightened portion, in contrast, an amount ofeccentricity was greater than 0.05 mm, and accordingly, both ofroundness and cylindricity were rated “B”.

Comparative Example: Cast Iron was Processed with CBN Sintered Body

TABLE 4 Amount Sample of eccen- Round- Cylin- No. Tool tricity mm nessdricity 7 Without lightened portion 0.085 B B 8 Without lightenedportion 0.051 B B 9 With lightened portion 0.048 A A 10 With lightenedportion 0.035 A A 11 With lightened portion 0.028 AA AA 12 Withlightened portion 0.012 AA AA

Reamers 90 (samples 7 and 8) of the shape of reamer 90 of Embodiment 1without lightened portion 29 were prepared. Core 80 is made of cementedcarbide. Hard tool insert 19 is made of CBN sintered body.

An amount of eccentricity in reamer 90 (a distance from the axis ofrotation to the position of the center of gravity of reamer 90) wasmeasured.

Samples 7 and 8 have amounts of eccentricity shown in Table 4.

Subsequently, a work test was performed using samples 7 and 8. FIG. 23is a plan view of a workpiece provided with holes. FIG. 24 is asectional view of the workpiece provided with the holes. As shown inFIGS. 23 and 24 , first, holes 101 were formed in workpiece 100 (FC250(JIS G 5501 1995)) with a drill. Holes 101 were processed with reamers90 being samples 7 and 8, to thereby form finished holes 102. Table 5shows the conditions for creating finished holes 102.

TABLE 5 Evaluation conditions Workpiece FC250 (JIS G 5501 1995) Cuttingfluid Water-soluble emulsion (8%) Blade diameter ϕ12.000 mm Cutting rateVc = 250 m/min Feed rate f = 0.25 mm/rev

The roundness and cylindricity of finished hole 102 were measured inaccordance with the requirements in JIS B0621 (1984) with a roundnessand cylindrical profile measuring instrument (e.g., RONDCOM 65Aavailable from Tokyo Seimitsu CO., LTD.). Measured data is a numericalvalue measured by the MZC method. Table 4 shows the results.

Table 6 shows the contents of evaluation criteria (AA, A, B) ofroundness and cylindricity in Table 4.

TABLE 6 Roundness Cylindricity B Not less than 5 μm B Not less than 6 μmA Not less than 3 μm and A Not less than 4 μm and less than 5 μm lessthan 6 μm AA Less than 3 μm AA Less than 4 μm

Example: Cast Iron was Processed with CBN Sintered Body

Reamers 90 (samples 9 to 12 in Table 4) of the shape of reamer 90 ofEmbodiment 1 with lightened portion 29 were prepared. Core 80 is made ofcemented carbide. Hard tool insert 19 is made of CBN sintered body.

An amount of eccentricity in reamer 90 (a distance from the axis ofrotation to the position of the center of gravity of reamer 90) wasmeasured. Table 4 shows amounts of eccentricity.

Subsequently, a work test was performed using samples 9 to 12. As shownin FIGS. 23 and 24 , first, holes 101 were formed in workpiece 100(FC250 (JIS G 5501 1995)) with a drill. Holes 101 were processed withreamers 90 being samples 9 to 12, to thereby form finished holes 102.Table 5 shows the conditions for creating finished holes 102.

The roundness and cylindricity of finished hole 102 were measured. Table4 show the results.

As shown in Table 4, in samples 9 to 12 provided with a lightenedportion, an amount of eccentricity was 0.05 mm or less, and accordingly,roundness and cylindricity were rated “A” or “AA”. It was found that insamples 7 and 8 without a lightened portion, in contrast, an amount ofeccentricity was greater than 0.05 mm, and accordingly, both ofroundness and cylindricity were rated “B”.

It should be understood that the embodiments and examples disclosedherein are illustrative and non-restrictive in every respect. The scopeof the present invention is defined by the terms of the claims, ratherthan the embodiments and examples above, and is intended to include anymodifications within the scope and meaning equivalent to the terms ofthe claims.

REFERENCE SIGNS LIST

-   -   11, 12, 13, 14, 15 outer-circumference cutting edge; 18 margin;        19 hard tool insert; 21, 22, 23, 24, 25 flute; 21 a terminal        end; 29 lightened portion; 80 core; 80 a blade effective region;        80 b balance adjustment region; 80 c chuck region; 81 oil hole;        82 front end; 85 center of rotation; 86 center of gravity; 87        shank; 87 a, 101 hole; 90 reamer; 100 workpiece; 102 finished        hole.

1. A reamer comprising: a core; and a plurality of outer-circumferencecutting edges provided on an outer circumference of the core and made ofa hard tool material, the core extending from a front end to a rear end,the core being provided with a plurality of flutes extending from thefront end to the rear end, a center-of-gravity adjustment portion beingprovided at least partially from terminal ends of the plurality offlutes on a rear end side to the rear end of the core, thecenter-of-gravity adjustment portion causing the distance from thecenter of rotation to the center of gravity to be smaller than when thecenter-of-gravity adjustment portion is not provided, wherein thecenter-of-gravity adjustment portion is the terminal ends of theplurality of flutes, the terminal ends being provided at differentpositions in an axial direction.